Septic Tank Inspection - How to Inspect Septic Tank Condition InspectAPedia® -
How to inspect the condition of a septic tank - detailed procedures
Septic tank inspection checklist
Types of Septic Tanks: steel septic tanks, concrete septic tanks, fiberglass septic tanks, home made septic tanks - definitions and characteristics of various types of septic tanks
Inspection specifics each different type of septic tank
Inspection specifics for septic tank baffles, septic tank sludge and scum levels or thickness
Questions & answers about "how do you inspect or test a septic tank?"
How to inspect the septic tank: This document describes in detail how to inspect the condition of a septic tank - a key component in
onsite wastewater disposal systems.
After discussing a list of things to watch for before, during, and after pumping or cleaning out
a septic tank, we discuss specific septic system inspection details and concerns for
steel septic tanks, concrete septic tanks, home made septic tanks, fiberglass or plastic septic tanks, and the condition of
septic tank baffles.
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Also see SEWAGE LEVELS in SEPTIC TANKS for an a discussion of: What Do the Levels of Sewage in the Septic Tank Mean about Septic Tank Condition, Septic Tank Leaks, & the Timing of Septic Tank Pumping.
Detail about septic tank tees and baffles is at SEPTIC TANK BAFFLES.
This is a chapter of Septic Systems Inspection, Testing our online book about septic system inspection procedures,
defects in onsite waste disposal systems, septic tank problems, septic
drainfield problems, checklists of system components and things to ask.
INSPECTING TANKS - How to Inspect the Condition of A Septic Tank
The purpose of the treatment tank or "septic tank" is to contain solid waste and to permit the beginning of
bacterial action to process sewage into a combination of clarified effluent, settled sludge, or floating scum in the
tank. An intact, un-damaged septic tank is normally always filled with these materials. However the inspector
performing a "visual" check of the septic system needs to be alert
for some important findings which we describe below.
How to Inspect the Septic Tank Before & After Pumping
If you have not already reviewed
SEPTIC TANK SAFETY please
do so before continuing in this section. There are serious risks of injury, explosion, and
death if safe procedures are not followed when working on septic systems.
Septic Tank Safety Warnings
Don't work alone: Falling into a septic tank or even leaning over a septic tank can be fatal.
Do not work on or at septic tanks alone - workers can become suddenly overcome by methane gas.
Do not ever go into a septic tank to inspect or repair it unless you are specially trained and are wearing the
special equipment and gear for that purpose, including self-contained breathing apparatus.
Don't enter the septic tank to rescue someone: Never go into a septic tank to retrieve someone who has fallen in and was overcome by toxic gases
without a self-contained breathing apparatus (SCBA). if a SCBA is not available, call for emergency services and put a
fan at the top of the tank to blow in fresh air.
Don't even lean over the septic tank openings: Do not lean over or stick your head into the septic tank to examine its interior - you could fall in to the
tank or become overcome by gases and fall into the tank, an event which is likely to be fatal.
Don't ignite flames near the septic tank: Do not light a flame at or near the tank - methane gas is explosive. At one tank pumpout my client described
the explosion and burns received by the pumping contractor when he stood by the tank and lit a cigarette. Another exploded their septic tank by burning brush that was piled over the tank.
Work area around the septic tank must be ventilated: Decomposing wastes in the septic tank produce toxic gases (such as methane) which
can kill a human in a matter of minutes. When working on a tank be sure the area is well ventilated.
Rope off Dangerous Septic Tanks, Cesspools, Drywells, Work Sites: If your inspection discover that there are dangerous conditions, such as
an unsafe tank cover, tank collapse, or a home-made septic tank or cesspool (which are at increased risk of sudden collapse)
such areas should be roped off and clearly marked as dangerous to prevent access until proper evaluation and repairs can be made.
If you have not already reviewed SEPTIC TANK SAFETY please
do so before continuing in this section. There are serious risks of injury, explosion, and death if safe procedures are not followed when working on septic systems.
A SEPTIC TANK INSPECTION CHECKLIST
Inspecting the Septic Tank and Septic Tank Area Before Opening the Septic Tank
Subsidence (depressions or low areas in the soil) at the septic tank location - may risk dangerous, potentially fatal collapse
Evidence of recent work which may need to be investigated to understand the condition of the septic system
Evidence of backup or effluent breakout at the surface in the septic tank area (also see SEPTIC TANK GRASS or SNOWMELT)
Condition of the Septic Tank Covers: Condition and safety of the tank and access covers.
In the photo shown here
a round concrete septic tank cover was placed over collapsing concrete blocks stacked to provide an access to a septic tank.
There was a septic tank collapse risk and a possible fatal hazard which at this property was an area only three meters
from a children's playground.
The stacked concrete blocks were tumbling and the opening into the septic tank was larger
than the cover. We covered the area with plywood, roped it off, and informed the appropriate parties including the property owner.
A safe septic tank cover on a concrete tank is shown in a photo below where we discuss
concrete septic tanks.
Inspecting the Septic Tank After Opening the Septic Tank but Before Pumping
After Opening But Before Pumping the Septic Tank: When the septic tank is opened before it has been pumped out or cleaned, important information about the condition of
the septic system is available:
Thickness of scum and sludge levels: Septic tank maximum scum and sludge buildup prior to pump out, and instructions for measuring the floating scum
layer thickness and settled sludge layer thickness in a septic tank are available in a separate chapter at Septic Tank Pumping Guide. At SEWAGE LEVELS in SEPTIC TANKS we explain the meaning of thick or thin scum or sludge levels and high or low levels of sewage in the septic tank.
Back-flow of effluent into the tank during pumpdown - an indicator of flooded leach fields
Condition of the Septic Tank Baffles: damage to the tank baffles. Evidence of a broken concrete septic tank baffle
is shown below at our discussion of home made site built tanks, and a rusted-steel septic tank baffle is shown
in other photographs on this page. See SEPTIC TANK BAFFLES for an explanation of how to observe clues at the septic tank baffles or tees to look for signs of tank flooding when opening the septic tank for cleaning, pumping, or inspection.
Liquid and waste level in the tank: evidence of waste passing over the baffles - a flooded system, an indicator of septic system failure.
Evidence of sewage flowing over the septic tank baffle is shown in a photo below where we describe septic tank baffles.
Unusually high levels of sewage in the septic tank - suggesting a blocked outlet or drainfield. The drainfield may be failing due a damaged or clogged pipe, a clogged, failing drainfield, or due to groundwater leaks into the septic tank or groundwater that saturates the drainfield.
Unusually low levels of sewage in the septic tank - suggesting that the tank has a leak, can have several causes depending on the tank age and the material from which it was built.
Low Sewage Levels in Concrete septic tanks: If the tank is made of concrete
it should be pumped and cleaned thoroughly so that your contractor can inspect the tank for cracks or other damage.
Low Sewage Levels in Plastic/Fiberglass septic tanks: after pumping the tank, look for a lost drain plug in the tank
bottom. Even pumping the tank can accidentally remove this plug - a condition you won't notice until the next time it's pumped.
Low Sewage Levels in Steel Septic Tanks: Pump the tank completely, clean and inspect for rust holes - it's common for the
bottom of such tanks to rust completely away.
Low Sewage Levels in Home Made or Site Built Septic Tanks: there is risk of tank collapse or leaks when septic tanks
are site-built such as using concrete blocks or stone. Leaks are likely
See Septic Tank Leaks - for an explanation of how and why septic tank leaks cause septic system failures.
See SEWAGE LEVELS in SEPTIC TANKS for an a discussion of: What Do the Levels of Sewage in the Septic Tank Mean about Septic Tank Condition, Septic Tank Leaks, & the Timing of Septic Tank Pumping.
Septic Tank Inspection During Tank Pumping
During Septic Tank Pumping: if the pumper observes (or hears) septic effluent flowing back into the septic tank
from the tank outlet pipe this is a sure indication that the drainfield or soil absorption system is waterlogged, and
indicates a system failure needing further investigation.
The photo shows a concrete septic tank during pumping. As the effluent level dropped
below that of the bottom of the tank baffles, we stopped pumping briefly to listen for the sound of effluent flowing back into the
tank from its outlet.
Septic tank pumping is best performed from an access cover at the center of the tank if one is provided (as in this photo).
This gives best access to the pumper to clean sludge and debris from all areas of the tank bottom.
Septic Tank Inspection After the Septic Tank has Been Pumped Out
Only by pumping and visual inspection can actual tank capacity and condition be
completely determined. Probing in the area of a tank, without excavation, is not recommended as the probe may damage a steel or fiberglass tank.
When a tank is uncovered for pumping additional critical details may be observed before the pumping operation begins
After the septic tank has been pumped out it may be useful to inspect its interior for evidence of cracks, settlement,
or damage to its baffles, or perhaps to confirm the tank size if most of the tank has remained buried.
If a septic tank has been serviced by removing a cover over the entire tank all of these conditions can
be seen easily. But more often the tank is pumped by access through a center cleanout port.
If there is no center cleanout port on a septic tank (some older concrete tanks) it is pumped preferably at the outlet end of the tank but
possibly at the inlet end. Septic pumpers may use a tool such as the one shown here,
a combination of a mirror at the end of a pole and a flashlight to look at the tank interior.
Look for Evidence of damage to the tank itself such as cracks, leaks, or additional evidence of damaged tank baffles.
SAFETY WARNING: Do not enter
or lean down over or into any septic tank unless you're wearing special breathing apparatus and have
a second worker watching you for safety - methane gas in the tank can cause fatal asphyxiation.
It should never be necessary to enter a septic tank. Any work to replace the baffles
or repair the tank should be done from the outside.
SEPTIC TANK SOLIDS & SCUM - thickness, net free area, effluent retention time
Solids entering a septic tank are intended to remain there until pumped out during tank service. A large
portion of solids settle to the bottom of the tank as sludge.
Grease and floating scum remain at the top of the
sewage in the tank. Baffles (discussed above) help keep solids, scum, and grease in the tank. Bacterial action
in the tank make a modest reduction in the solids volume and begin the processing of sewage pathogens, a step
later completed by soil bacteria in the absorption fields.
A separate document, MEASURE SCUM & SLUDGE,
discusses how and why to measure septic tank scum and sludge
Net free area: If the sludge level becomes too high or the floating scum layer too thick, in addition to risking passage of
solids out of the tank (damaging the absorption system), the remaining "net free area" of liquid in the tank is reduced.
When the net free area becomes too small, there is insufficient time for waste entering the tank to settle out as
bottom sludge or top floating scum. The time allowed for sewage to separate and settle out as sludge or
collect as floating scum is called septic tank retention time. Retention time is discussed further at
EFFLUENT RETENTION TIME
"Septic Effluent Retention time and Effective Septic Tank Volume - Why pump a septic tank before it is "full" of solids and grease?".
For an in-use septic tank with a small net free area, and therefore a short septic effluent retention time, the frequent entry of
solid and liquid waste will keep the tank debris agitated, thus forcing floating debris into the absorption system where the
life of that component will be reduced (due to soil clogging).
The importance of keeping an adequate net free area in a septic tank is the reason that tanks need to be pumped
at regular intervals. Building owners who never pump a tank until it is clogged have already damaged the
absorption system and reduced its future life expectancy.
Frequently-Asked Questions (FAQs) about septic tank inspection procedures:
Question: My septic tank was cleaned out, then received about two feet of wastewater - the level never dropped. Is something wrong?
I had my septic tank emptied and left the lid off so I could monitor what was going on . soon there was 2 feet of liquid in it .. I then left town for 2 weeks and when I came back , the 2 foot level had not dropped at all ... if this tank is a 2 compartment tank does that mean that the water level must get a lot higher to spill over to the part of the tank that heads to the leach field ?
also , if that is true then by putting in liquid that would help clear up my leach lines wouldn’t do any good until the level is much higher ? can you give me any comments about this please ? thanks for the help. P.D.
Reply:
A competent onsite inspection of the septic tank by an expert usually finds additional clues that help accurately diagnose a problem with the tank, its baffles, piping, or the septic drainfield. That said,
Watch out: you should never leave the lid off of a septic tank. Doing so risks killing someone. Anyone, adult or child, who falls into an open septic tank is likely to die very quickly due to asphyxiation from methane and other gases in the tank. Details are at SEPTIC SYSTEM SAFETY WARNINGS
Now, a properly functioning septic tank is water tight. The liquid or sewage or wastewater level in the septic tank won't drop below the tank outlet opening unless the tank is damaged and leaking. A normal septic tank is always full of waste up to a level just below the outlet opening.
In a two compartment septic tank the wall separating the two compartments will have an opening that allows liquid effluent to flow into teh second compartment, keeping floating scum and settled sludge in the first compartment (mostly). The entire tank, both compartments, will need to be filled with wastewater before any effluent will begin to flow out of the septic tank and into the drainfield or soakaway bed.
So when you observed about two feet of waste in the septic tank, then left the system unused, you'd expect to find exactly the same amount in the tank weeks later. Only a very slight drop in level might occur, less than an inch - caused by evaporation - because you left the tank open (and dangerous).
Please see SEWAGE LEVELS in SEPTIC TANKS for details about how to interpret abnormal levels of sewage found in the septic tank (too high or too low).
Questions & Answers regarding this article
Questions & answers about "how do you inspect or test a septic tank?"
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389
(2006), Advanced Onsite Wastewater Systems Technologies.
Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going
for homeowners but is a text we recommend for professionals--DF.
AEROBIC SEPTIC SYSTEMS
Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP;
Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.
Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.
Design Manuals for Septic Systems
US EPA Onsite Wastewater Treatment Systems Manua [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems,
Richard J Otis, published by the US EPA. Although it's more than 20 years old, this book remains a useful reference for septic system designers.
U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980)
"International Private Sewage Disposal Code," 1995, BOCA-708-799-2300, ICBO-310-699-0541, SBCCI 205-591-1853, available from those code associations.
"Manual of Policy, Procedures, and Guidelines for Onsite Sewage Systems," Ontario Reg. 374/81, Part VII of the Environmental
Protection Act (Canada), ISBN 0-7743-7303-2, Ministry of the Environment,135 St. Clair Ave. West, Toronto Ontario M4V 1P5 Canada $24. CDN.
Manual of Septic Tank Practice, US Public Health Service's 1959.
Onsite Wastewater Disposal Books
Onsite Wastewater Disposal, R. J. Perkins;
Quoting from Amazon: This practical book, co-published with the National Environmental Health Association,
describes the step-by-step procedures needed to avoid common pitfalls in septic system technology.
Valuable in matching the septic system to the site-specific conditions, this useful book will help you install a reliable system in
both suitable and difficult environments. Septic tank installers, planners, state and local regulators, civil and sanitary engineers,
consulting engineers, architects, homeowners, academics, and land developers will find this publication valuable.
Onsite Wastewater Treatment Systems, Bennette D. Burks, Mary Margaret Minnis, Hogarth House 1994 - one of the best septic system books around, suffering a bit from small fonts and a weak index. While it contains some material more technical than needed by homeowners, Burks/Minnis book on onsite wastewater treatment systems a very useful reference for both property owners and septic system designers.
Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf
Planting Over Septic System Component", Daniel Friedman (author/editor, InspectAPedia.com), The Innovator, Winter/Spring 2008, BCOSSA, British Columbia OnSite Sewage Association, 201-3542 Blansard St., Victoria BC V8X 1W3 Canada
Septic System Owner's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000 $14.95 U.S. - easy to understand, well illustrated, one of the best practical references around on septic design basics including some advanced systems; a little short on safety and maintenance. Both new and used (low priced copies are available, and we think the authors are working on an updated edition--DF.
Quoting from one of several Amazon reviews: The basics of septic systems, from underground systems and failures to what the owner can do to promote and maintain a healthy system, is revealed in an excellent guide essential for any who reside on a septic system. Rural residents receive a primer on not only the basics; but how to conduct period inspections and what to do when things go wrong. History also figures into the fine coverage.
Test Pit Preparation for Onsite Sewage Evaluations, State of Oregon Department of Environmental Quality, Portland OR, 800 452-4011. PDF document. We recommend this excellent document that offers detail about soil perc tests, deep hole tests, safety, and septic design. Readers should also see Soil Percolation Tests and for testing an existing septic system, also see Dye Tests
Grass is Always Greener Over the Septic Tank, Bombeck, Erma: $ 5.99; FAWCETT; MM;
This septic system classic whose title helps avoid intimidating readers new to septic systems, is available new or used at very low prices.
It's more entertainment than a serious "how to" book on septic systems design, maintenance, or repair. Not recommended -- DF.
US EPA Onsite Wastewater Treatment Systems Manual Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm
Water Wells and Septic Systems Handbook, R. Dodge Woodson. This book is in the upper price range, but is worth the cost for serious septic installers and designers.
Quoting Amazon: Each year, thousands upon thousands of Americans install water wells and septic systems on their properties. But with a maze of codes governing their use along with a host of design requirements that ensure their functionality where can someone turn for comprehensive, one-stop guidance? Enter the Water Wells and Septic Systems Handbook from McGraw-Hill. Written in language any property owner can understand yet detailed enough for professionals and technical students this easy-to-use volume delivers the latest techniques and code requirements for designing, building, rehabilitating, and maintaining private water wells and septic systems. Bolstered by a wealth of informative charts, tables, and illustrations, this book delivers: * Current construction, maintenance, and repair methods
* New International Private Sewage Disposal Code
* Up-to-date standards from the American Water Works Association
Wells and Septic Systems, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992. We have found this text very useful for conventional well and septic systems design and maintenance --DF.
Quoting an Amazon description:Here's all the information you need to build a well or septic system yourself - and save a lot of time, money, and frustration. S. Blackwell Duncan has thoroughly revised and updated this second edition of Wells and Septic Systems to conform to current codes and requirements. He also has expanded this national bestseller to include new material on well and septic installation, water storage and distribution, water treatment, ecological considerations, and septic systems for problem building sites.
The NSFC Products List has an excellent list of design manuals/modules available from their website or by telephone 800-624-8301
Submissions welcome. send us a suggested document link or request an exchange of website links
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